Pilot valve comprising a valve seat arrangement

ABSTRACT

Pre-controlled valve, in particular an electropneumatic regulating valve for an air brake system of a motor vehicle, comprising a valve housing ( 1 ), which contains an axially adjustable control piston ( 5 ) and which can be actuated by means of at least one electromagnetic pilot valve ( 6 ) for axial adjustment, and which is provided to actuate a valve seat assembly ( 9 ), which switches the compressed air flow between at least one external brake line connection ( 15 ), a feed pressure connection, as well as a venting port ( 17 ), and which comprises in essence a pot-like sealing cup ( 12 ) with a coaxial passage ( 23 ), the circular ring-shaped sealing area ( 13 ) of which corresponds with a coaxial valve seat assembly, constructed out of an external valve seat ( 11 ) and an internal valve seat ( 10 ), whereby the sealing cup ( 12 ) exhibits an internal reinforcing insert ( 24 ), which is formed essentially in the shape of a U according to the cross section of the edge and which is provided with a molded-on shoulder ( 25 ), which is oriented radially towards the inside and reinforces the inside radial area of the sealing area ( 13 ), whereby the two legs ( 26, 27 ) of the reinforcing insert ( 24 ) project reinforcingly into the respectively assigned sealing lip segments ( 26, 27 ) of the sealing cup ( 12 ).

[0001] The present application is a continuation of International PatentApplication No. PCT/EP02/04632, filed Apr. 26, 2002, designating theUnited States of America and published in German as WO 02/102636, theentire disclosure of which is incorporated herein by reference. Priorityis claimed based on Federal Republic of Germany Patent Application No.101 20 322.5, filed Apr. 26, 2001.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] The invention relates to a pre-controlled valve, in particular anelectropneumatic regulating valve for an air brake system of a motorvehicle.

[0003] The electropneumatic regulating valve of the present inventioncomprises a valve housing, which contains an axially adjustable controlpiston and which can be actuated by means of at least oneelectromagnetic pilot valve for axial adjustment, and which is providedto actuate a valve seat assembly, which switches the compressed air flowbetween at least one external brake line connection, a feed pressureconnection, as well as a venting port, and which comprises in essence apot-like sealing cup with a coaxial passage, the circular ring-shapedsealing area of which corresponds with a coaxial valve seat assembly,constructed out of an external valve seat and an internal valve seat. Inparticular the present invention relates to a special configuration ofthe sealing cup.

[0004] The generic pre-controlled valve is installed inside an air brakesystem of a utility vehicle, for example, as an electropneumaticregulating valve, in order to correct a brake pressure in accordancewith the desired braking effect. For this purpose a brake line, issuingfrom the regulating valve, is connected usually to a brake cylinder,which is disposed at the vehicle wheel and which produces the necessarybrake force for a disk or drum brake, attached to said wheel, for thepurpose of braking. The desired pressure value for the electropneumaticregulating valve can be specified both electrically and alsopneumatically. However, the pneumatic drive is used only for safety inthe case the electric drive fails.

[0005] One such electropneumatic regulating valve is known from the DE196 05 562 A1. The regulating valve exhibits a control piston, which hasa large area and is housed inside a valve housing and which can be movedaxially over a corresponding control chamber. Opposite the controlchamber, the control piston borders on a working chamber. On the side ofthe working chamber, a coaxial hollow pin is formed on the controlpiston, which serves to actuate an adjacent valve seat assembly. Thevalve seat assembly switches, by means of an axial adjustment of aspring-stressed sealing cup, the compressed air flow between an externalbrake line connection, a feed pressure connection as well as a ventingport.

[0006] The control piston can be actuated by way of a pilot valveassembly with a control pressure from the side of the control chamber.The pilot valve assembly comprises here two electromagnetic pilotvalves, which affect, by means of a coordinated flow around theintegrated electric coils, an increase, hold, or decrease in the controlpressure inside the control chamber. On the side opposite the controlpiston, a counterforce, resulting from the brake pressure, is effective.

[0007] The valve seat assembly, which can be actuated in such a mannerby the control piston, envelops the pot-like sealing cup, which isprovided with a coaxial passage, in order to lead the exhaust air,accumulated while venting the control chamber, through said passage tothe venting port. The remaining circular ring-shaped sealing area of thesealing cup forms together with an opposite external valve seat, whichenvelops a coaxial internal valve seat, a corresponding valve seatassembly.

[0008] The compressed air of the brake line connection, connected to theworking chamber, is supplied by depressing the sealing cup, whereby saidsealing cup lifts off from the external valve seat so that an air flowfrom the feed pressure connection to the working chamber is released. Aventing of the working chamber, connected to the brake line connection,is achieved by raising the internal valve seat, which is made as onepiece with the control piston, with the result that the compressed airflows starting from the working chamber to the venting port.

[0009] The quality of control achieved with the prior art valve seatassembly that is described above is limited by a relatively large forcecomponent, which acts from the bottom on the sealing cup in thedirection of the control piston, and which is generated in essence bythe influences of the brake pressure. Opposite this bottom forcecomponent there is on the other side of the sealing cup an upper forcecomponent, which exhibits a smaller amount due to a smaller effectivesurface—caused by the coaxial arrangement of both valve seats—inconnection with the pressure in the working chamber in the closed valveposition. This imbalance of the two force components results in arelatively large hysteresis of the valve seat assembly, a feature thathas a negative impact on the quality of control.

[0010] Attempts have already been made to enlarge the effective circularring-shaped sealing area of the sealing cup by decreasing further thediameter of the piston seat. However, it has turned out that the sealingcup is stressed so unfavorably in the area of the inside rim that noreliable tightness and no exact valve function can be obtained.Enlarging the external valve seat cannot be considered because ofdesign-related restrictions.

[0011] The sealing cup is made of an elastomer and exhibits areinforcing insert, which is formed essentially at right angles inaccordance with the cross section of the edge, whereby the horizontalleg, running below the sealing area, connects to a vertical leg,extending along an external sealing lip segment, in order to reinforcein this respect the external flank of the sealing cup. Given the edgeconditions described above, this geometry does not result in anenlargement of the force component above the sealing cup. In the extremecase the impact of the internal valve seat can result in a shearing offof the sealing material on the sealing cup.

[0012] Therefore, the object of the present invention is to furtherimprove a generic pre-controlled valve to the effect that the sealingcup, used in connection with the valve seat assembly, makes it possibleto decrease the internal diameter of the valve seat in order to increasethe force component above the sealing cup and simultaneously ensures areliable sealing function during continuous operation.

[0013] The problem is solved, according to the invention, starting froma pre-controlled valve comprising a valve housing containing an axiallyadjustable control piston which can be actuated by at least oneelectromagnetic pilot valve, and which actuates a valve seat assembly toswitch compressed air flow between at least one external brake lineconnection, a feed pressure connection, and a venting port, wherein thevalve seat assembly includes a pot-like sealing cup with a coaxialpassage, The sealing cup includes an internal reinforcing insert, whichis formed essentially in the shape of a U according to the cross sectionof the edge and which is provided with a molded-on shoulder, which isoriented radially towards the inside and reinforces the inside radialarea of the sealing area, whereby the two legs of the reinforcing insertproject reinforcingly into the respectively assigned sealing lipsegments of the sealing cup.

[0014] An advantage of such a designed sealing cup lies in the fact thatthe critical area of the sealing area that corresponds with the internalvalve seat is supported in such a manner by an especially facilitatinggeometry of the reinforcing insert that the diameter of the valve seatcan be reduced even further in order to enlarge in this respect theeffective ring area above the sealing cup without impeding the axialmoveability of the sealing cup. As a consequence, a smaller valvehysteresis is achieved, a feature that results in a better controlquality of an electropneumatic regulating valve.

[0015] Preferably the reinforcing insert is made of a relatively rigidplastic, as compared to the enveloping elastomeric sealing material ofthe sealing cup, and which is vulcanized into the sealing cup. Inaddition, it is also conceivable to use a reinforcing insert made ofsteel, aluminum, or the like.

[0016] According to another embodiment of the invention, the tworing-shaped sealing lip segments, issuing from the sealing lip cup, aredesigned approximately the same length in order to guarantee a uniformquality of sealing in interaction with the legs of the reinforcinginsert, said legs being also of equal length, without the differentcontact forces on the housing components, which correspond to thesealing cup, resulting in the axial moveability of the sealing cup beingimpeded.

[0017] According to a further embodiment of the invention, a tubesegment with a venting duct can be run through the passage in thesealing cup, in order to guide the exhaust air, accumulated whileventing the control chamber, directly into the area of the venting port.Correspondingly the diameter of the passage is matched with the diameterof the tube segment in such a manner that a circular ring-shaped flowcross section, which is just adequate enough to vent the workingchamber.

[0018] Other objects, advantages and novel features of the presentinvention will become apparent from the following detailed descriptionof the invention when considered in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a longitudinal cross-section view through anelectropneumatic regulating valve with a sealing cup in accordance withan embodiment of the invention.

[0020]FIG. 2 is a detailed longitudinal cross-section view in the areaof the valve seat assembly of the embodiment of FIG. 1; and

[0021]FIG. 3 is a separate longitudinal cross-section view through thesealing cup of the embodiment of FIG. 1.

DETAILED DESCRIPTION

[0022] The electropneumatic regulating valve, according to FIG. 1,includes a two-part housing, which comprises a bottom relay valvehousing 1, which is connected by means of a screw connection to an upperpilot valve housing 2 by way of a sealing element 3, which liesin-between. The relay valve housing 1 and the pilot valve housing 2enclose an internal cavity, which is formed as a control chamber 4, andin which a control piston 5 is disposed so as to move axially. For axialadjustment of the control piston 5, there is a pilot valve assembly,which is housed in the pilot valve housing 2 and of which here only onepilot valve 6, serving as the outlet magnet, is shown. The pilot valveassembly is driven electrically by means of an electronic unit 7, whichis also disposed in the pilot valve housing 2.

[0023] The illustrated pilot valve 6 vents upon actuation of the controlchamber 4, whereby the accumulated exhaust air is bled off to theatmosphere by way of a coaxial venting duct 7. In addition to the pilotvalve 6, serving as the outlet valve, there is a second pilot valve (notshown here) as the inlet valve, which serves to actuate the controlchamber 4 with a control pressure in order to adjust axially the controlpiston 5.

[0024] As a consequence of actuating the control chamber 4, the controlpiston 5 actuates by means of a bottom sleeve-like coaxial attachment avalve seat assembly 9. The distal end of the coaxial attachment isdesigned as the internal valve seat 10. In addition to the internalvalve seat 10, there is an external valve seat 11, which is disposedcoaxially in the same plane and which is arranged stationarily oppositethe relay valve housing 1. Both valve seats 10 and 11 act together witha pot-like sealing cup 12, the sealing area 13 of which rests againstthe two valve seats 10 and 11 in a closed switching position of theregulating valve, which takes place, among other things, due to theeffect of a pressure spring 14, disposed between the relay valve housing1 and the sealing cup 12. Above this valve seat assembly 9 the air flowcan be switched, on the one hand, between a brake line connection 15,which is disposed on the relay valve housing 1, and a feed pressureconnection (cannot be seen here), which is connected to an internal feedpressure chamber 16, and, on the other hand, a venting port 17. Theventing port 17 is additionally provided with a sound absorber 18 todecrease the noise of the working chamber 19, which can be connected tothe brake line connection 15, as well as the exhaust air, flowing out ofthe venting duct 8.

[0025] The electropneumatic regulating valve is shown here in its closedswitching position. Upon actuation of the control chamber 4 with acontrol pressure and subsequent movement of the control piston 5 in thedirection of a bottom position, compressed air, issuing from the feedpressure chamber 16, flows, upon opening the external valve seat 11, byway of the working chamber 19, to the brake line connection 15, in orderto increase in this respect the brake pressure.

[0026] In venting the control chamber 4, the control piston 5 isconveyed into an upper position, thus opening the internal valve seat10, so that starting from the brake line connection 15, the compressedair flows by way of the working chamber 19 to the venting port 17, inorder to reduce correspondingly the brake pressure. Thus, the brakepressure is influenced here by a reciprocating movement of the controlpiston 5.

[0027] As follows from the detailed drawing according to FIG. 2, thesealing cup 12 of the valve seat assembly 9 exhibits an internal radialsealing lip segment 20 as well as an external radial sealing lip segment21, both of which rest sealingly against tube-shaped segments of aninsert sleeve 22, which is arranged stationarily opposite the relayvalve housing 1, and encloses the spring 14. A tube segment 24,containing the venting duct 8, runs through a passage 23 in the sealingcup 12, in order to guide the exhaust air, accumulated while venting thecontrol chamber (not illustrated here), into the area of the ventingport.

[0028] According to FIG. 3, the sealing cup 12 has an internalring-shaped reinforcing insert 24, which is designed essentially in theshape of a U according to the cross section of the edge. The reinforcinginsert 24 is made here of a relatively rigid plastic, as compared to theelastomeric sealing material of the sealing cup 12, and is incorporatedby vulcanizing into the sealing cup 12. The reinforcing insert 24 isprovided with a shoulder 25, which is oriented radially towards theinside, in order to reinforce additionally the inside radial area of thesealing area 13. Two legs 26 and 27 of the reinforcing insert 24 projectinto the respective two sealing lip segments 20 and 21, in order toincrease the stability properties of the sealing cup 12 and to improvein this respect the sealing properties. The two sealing lip segments 20,21 of the sealing lip cup 12 are designed here the same length and acttogether with also equally long, but shorter legs 26, 27 of the internalreinforcing insert 24.

[0029] The foregoing disclosure has been set forth merely to illustratethe invention and is not intended to be limiting. Since modifications ofthe disclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof. For example, the length and diameterratios of the sealing cup can vary in the scope of the protection.

What is claimed is:
 1. An electropneumatic regulating valve for an airbrake system of a motor vehicle, comprising a valve housing, whichcontains an axially adjustable control piston which can be actuated byat least one electromagnetic pilot valve for axial adjustment, and whichis provided to actuate a valve seat assembly, to switch compressed airflow between at least one of an external brake line connection, a feedpressure connection, and a venting port, said valve seat assemblyincluding a pot-like sealing cup with a coaxial passage, and a circularring-shaped sealing area which corresponds to a coaxial valve seatarrangement formed by, an external valve seat and an internal valveseat, wherein the sealing cup includes an internal reinforcing insert,which is formed essentially in the shape of a U according to the crosssection of the edge and which is provided with a molded-on shoulder,which is oriented radially towards the inside and reinforces the insideradial area of the sealing area, whereby the two legs of the reinforcinginsert project reinforcingly into respective sealing lip segments of thesealing cup.
 2. An electropneumatic valve, as claimed in claim 1,wherein the reinforcing insert is made of a relatively rigid plastic, ascompared to the elastomeric sealing material of the sealing cup, andwhich can be vulcanized into the sealing cup.
 3. An electropneumaticvalve, as claimed in claim 1, wherein the reinforcing insert is made ofsteel or aluminum.
 4. An electropneumatic valve, as claimed in claim 1,wherein the sealing lip segments of the sealing lip cup areapproximately the same length and interact with are reinforced along aportion of their length by the legs of the internal reinforcing insert,said legs being also of equal length, and shorter than the length of thesealing lip, segments.
 5. An electropneumatic valve, as claimed in claim1, wherein a tube segment with a venting duct runs through the passagein the sealing cup, in order to guide exhaust air, accumulated whileventing a control chamber, directly into the area of the venting port.6. An electropneumatic valve, as claimed in claim 2, wherein a tubesegment with a venting duct runs through the passage in the sealing cup,in order to guide exhaust air, accumulated while venting a controlchamber, directly into the area of the venting port.
 7. Anelectropneumatic valve, as claimed in claim 3, wherein a tube segmentwith a venting duct runs through the passage in the sealing cup, inorder to guide exhaust air, accumulated while venting a control chamber,directly into the area of the venting port.
 8. An electropneumaticvalve, as claimed in claim 4, wherein a tube segment with a venting ductruns through the passage in the sealing cup, in order to guide exhaustair, accumulated while venting a control chamber, directly into the areaof the venting port.
 9. An electropneumatic regulating valve for an airbrake system of a motor vehicle, comprising: a valve housing; an axiallyadjustable control piston disposed in the valve housing and adapted tobe actuated by at least one electromagnetic pilot valve for axialadjustment; and a valve seat assembly actuated by the axially adjustablecontrol piston to switch compressed air flow between at least one of anexternal brake line connection, a feed pressure connection, and aventing port, wherein said valve seat assembly includes a coaxial valveseat arrangement formed by an external valve seat and an internal valveseat, and a sealing cup, the sealing cup including a ring-shaped sealingarea adapted to seal a gap between the external valve seat and theinternal valve seat, two coaxial sealing lip segments project from aface of the ring-shaped sealing area opposite the coaxial valve seats, aU-shaped internal reinforcing insert disposed in an annular gap betweenthe coaxial sealing lip segments, wherein the reinforcing insert has acenter section reinforcing the sealing area, two legs, each legreinforcing a corresponding sealing lip segment, and a shoulderprojecting radially inward and reinforcing an inside radial area ofsealing area, and a coaxial passage.
 10. The electropneumatic valve ofclaim 9, wherein the sealing cup is formed from an elastomeric sealingmaterial, and the reinforcing insert is formed from a plastic materialwhich is more rigid than the elastomeric sealing material.
 11. Theelectropneumatic valve of claim 10, wherein the reinforcing insert isvulcanized into the sealing cup.
 12. The electropneumatic valve of claim9, wherein the reinforcing insert is made of steel or aluminum.
 13. Theelectropneumatic valve of claim 9, wherein the sealing lip segments areof equal length, the reinforcing insert legs are of equal length andshorter than the sealing lip segments, and the sealing lip segments arereinforced along a portion of their length by the reinforcing legs. 14.The electropneumatic valve of claim 9, wherein a tube segment with aventing duct which vents a control chamber directly to the venting portis disposed through the sealing cup coaxial passage.
 15. Theelectropneumatic valve of claim 10, wherein a tube segment with aventing duct which vents a control chamber directly to the venting portis disposed through the sealing cup coaxial passage.
 16. Theelectropneumatic valve of claim 11, wherein a tube segment with aventing duct which vents a control chamber directly to the venting portis disposed through the sealing cup coaxial passage.
 17. Theelectropneumatic valve of claim 12, wherein a tube segment with aventing duct which vents a control chamber directly to the venting portis disposed through the sealing cup coaxial passage.
 18. Theelectropneumatic valve of claim 13, wherein a tube segment with aventing duct which vents a control chamber directly to the venting portis disposed through the sealing cup coaxial passage.